The aim of this study is to determine whether addition of an exercise program to a regimen of dietary adjustment and weight loss may increase the degree of reversal of insulin resistance or defects of insulin secretion in overweight patients with Type II, non-insulin-dependent diabetes mellitus. They will be characterized by the following tests and measurements: historical data base, body composition by underwater weighing, adipocyte counting and sizing, insulin response to intravenous glucose, to arginine infusion, and to a standard meal, glucose disposal rate by glucose clamp technique, hepatic glucose output by infusion of di-deutero-glucose, and stress testing with measurement of VO2 max. Subjects will then be randomized either to a regimen of accelerated weight loss with a hypocaloric diet high in complex carbohydrate and fiber or to the same plus a program of physical training. After training, the baseline studies will be repeated.